Equivalence (6)
I believe the answer is:
parity
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">equivalence</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that parity is a type of equivalence)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for parity that I've seen before include "Equality in status" , "Equality, equivalence" , "Equal condition" , "Beginner" , "Correspondence" .)